EP1711773A1

EP1711773A1 - Heat exchanger pipe, heat exchanger and use thereof

Info

Publication number: EP1711773A1
Application number: EP05701250A
Authority: EP
Inventors: Friedhelm Schmitz
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2004-02-03
Filing date: 2005-01-28
Publication date: 2006-10-18
Also published as: US8240364B2; EP1562018A1; CN100516762C; WO2005075926A1; CN1930442A; US20070131394A1; US7640969B2; US20100037611A1

Abstract

According to the invention, in order to prevent a film from forming which obstructs the transfer of heat in heat exchanger pipes (1, 23), the heat exchanger pipe (1, 23) comprises an external side (4) which is adjacent to the external surface (3) and which is impinged upon by a steam medium, and an inner side (6) which is adjacent to an inner surface (5) and which is impinged upon by a coolant, such that the outer surface (3) is provided with a first layer (7) which reduces the adhesion of the steam on the outer surface (3) and/or the inner surface is provided with a second layer (9) which reduces the adhesion of a coolant to the inner surface (5) and which is embodied as a biocidal layer. The invention relates to a heat exchanger (17) and to the use thereof.

Description

description

Heat exchanger tube, heat exchanger and use

The invention relates to a heat exchanger tube with an outer surface lying on the outside for exposure to steam and an inner surface lying on the inside for exposure to a cooling medium. The invention further relates to a heat exchanger with a cooling medium duct and a steam medium duct, the cooling medium duct having a multiplicity of heat exchanger tubes for guiding cooling medium on the inside of a heat exchanger tube, and the steam duct being designed to apply steam medium to an outside of a heat exchanger tube. The invention also leads to use.

Heat exchangers of the above type generally serve to transfer the heat contained in a fluid vapor medium to a fluid cooling medium. In this way, the vapor medium cools down while the cooling medium heats up. If necessary, the heat exchanger is designed so that the cooling of the steam medium leads to condensation of the steam medium - in this case, a heat exchanger is also referred to as a condenser, in particular a steam condenser. Heat exchangers, in particular condensers of the type mentioned, are usually installed in power plants. There, a fluid vapor medium generally serves as the working medium for driving a turbine and in the process delivers its kinetic energy for driving the turbine to a turbine rotor, which in turn serves to drive a generator.

Thereafter, a steam medium on the turbine outlet side is generally in a relaxed state, ie it has a pressure in the range of 1 bar and is hardly overheated. This steam medium on the turbine outlet side is generally fed to a heat exchanger, in particular a condenser of the type mentioned above. The goal is usually to condense medium, if necessary continue to use its heat content after delivery to the cooling medium.

The boundary of a steam medium guide in a heat exchanger of the above type is usually formed by a wall which is constructed from a multiplicity of heat exchanger tubes of the coolant guide. Other concepts provide cooling medium guides arranged transversely in a steam medium guide, so that a steam medium guided in the steam guide has to flow past the multiplicity of heat exchanger tubes of the cooling medium guide. The converted volume of such heat exchangers, in particular steam condensers, depending on the design, should be kept as low as possible and optimized so that the efficiency of such heat exchangers is as good as possible. The aim of a heat exchanger is therefore to make the heat transfer in a heat exchanger tube as effective as possible, so that the amount of heat contained in the steam medium can be supplied as completely as possible to the cooling medium and is not otherwise lost or unwantedly remains in the steam medium. A disability of the

Heat transfer takes place e.g. B. by forming an insulating condensation film on an outside of a heat exchanger tube. A hindrance to heat transfer is all the more serious the denser an insulating condensation film of this type is on an outer surface of a heat exchanger tube. The type of such a condensation film depends crucially on the drop formation or on the dripping behavior of condensed vapor medium.

A further impairment of the heat transfer is caused by the formation of a coating on the coolant side on the inside of a heat exchanger tube. Such a deposit is formed over time by the fact that inorganic and organic components contained in the cooling medium settle and accumulate on the inner surface of a heat exchanger tube. Various cleaning measures can have this effect slow down, but are complex and cannot prevent the process as such.

It would be desirable to have a heat exchanger tube and a use relating to the heat exchanger tube which provide improved heat transfer. It would also be desirable to have a heat exchanger with an improved efficiency, which is not unnecessarily impaired by a deteriorated heat transfer in a heat exchanger tube.

This is where the invention comes in, the task of which is to provide a heat exchanger tube, a heat exchanger and a use relating to a heat exchanger tube in which heat transfer from a vapor medium to a cooling medium is improved compared to conventional concepts.

The object is achieved with regard to a heat exchanger tube by a heat exchanger tube of the type mentioned at the outset, in which, according to the invention, the outer surface is provided with a first layer which reduces the adhesion of the steam medium to the outer surface and / or the inner surface is provided with an adhesion of the cooling medium to the Internal surface reducing second layer is provided, wherein the second layer is designed as a layer reducing the formation of deposits on the inner surface, wherein the second layer is designed as a biocide layer.

The invention is based on the consideration that the surface tension of the tube material is of great importance for the drop formation or the dripping behavior of a steam medium on the outer surface of the heat exchanger tube. In addition, the invention is based on the consideration that the formation of deposits on the inner surface of a heat exchanger tube depends to a large extent on the adhesive properties of the surface. In contrast to previously customary measures, which either provide for regular cleaning of the surfaces or additives in the steam / cooling medium, the invention has knows that it is possible, on the one hand to improve the surface tension of an outer surface, and on the other hand to improve the adhesive properties of an inner surface of a heat exchanger tube with regard to the requirements explained above, it is possible to adhere the vapor medium to the outer surface To provide the outer surface reducing first layer and / or to provide the inner surface with an adhesion of the cooling medium to the inner surface reducing second layer. This reduces the previously required complex cleaning measures on the inside of a heat exchanger tube and measures relating to additives in the cooling medium. On the outside of a heat exchanger tube, cleaning has disadvantageously not previously been common. Such measures provided with restrictions have so far been preferred, since it was previously not possible to provide heat exchanger tubes of the above type and, in particular, to provide them in a heat exchanger. One of the main reasons is that the pipes can only be coated with great effort after they have been manufactured. In addition, internal coatings can practically no longer be carried out after the pipes have been produced, since the pipes generally have a length of 10 m or more. A heat exchanger of the above type for a power plant usually has hundreds of kilometers of heat exchanger tubes installed. For a nuclear power plant, a heat exchanger can have more than 1000 km of heat exchanger pipes laid.

In addition to a coating of the base surface, that is to say the outer surface and / or the inner surface of the heat exchanger tube, a layer in the above sense also means a surface treatment of the surface of a heat exchanger tube provided with the claimed functionality. For example, the surface of a heat exchanger tube could be smoothed or polished by suitable measures. Prove to be much more effective in the sense of the above invention however, coating measures, which are explained below.

Advantageous further developments can be found in the subclaims and specify advantageous options for realizing a heat exchanger tube with regard to its surface design.

It is advisable to carry out a layer as a coating. The first layer and / or the second layer is particularly advantageously formed from a number of sublayers. Bottom layers can serve as adhesion promoter layers, for example. In order to improve the best possible adhesion of the layer reducing the adhesion of a fluid in the form of steam / cooling medium. In addition, a number of coating measures can be provided with regard to the smoothing or sealing of a surface and / or the adhesion-reducing layer.

It has proven to be particularly expedient that in the case of a two-sided coating of the heat exchanger tube, ie. H. a coating of the outer surface and a coating of the inner surface, the first layer is different from the second layer. The first layer is advantageous as the surface tension of the

Tube material designed on the outer surface reducing layer. A second layer is advantageously designed as a layer which reduces the formation of deposits on the inner surface of the tube material, that is to say it is designed to reduce the adhesive properties of the inner surface of a heat exchanger tube. It has been recognized in the course of the further development that the first layer on the steam side, due to its exposure to steam medium on the outside of the heat exchanger tube, is subject to different requirements than the second layer on the cooling medium side, to which cooling medium is applied on the inside of the heat exchanger tube. So the first and second layers can be optimize your requirements in different ways.

The first layer is therefore advantageously designed as a layer which reduces the surface tension of the outer surface. This advantageously reduces the formation of drops and the dripping behavior of the steam medium when it condenses.

An antifouling layer also proves to be advantageous. Such layers reduce the build-up and build-up of organic substances to a negligible extent. A layer with a toxic effect can also be applied to the inner surface. In particular, such a layer can be designed as a copper layer.

The invention leads to the achievement of the object with regard to the heat exchanger on a heat exchanger of the type mentioned at the beginning, in which a heat exchanger tube is designed according to the invention in a manner explained above.

It has proven to be particularly expedient that the heat exchanger tube is designed as a longitudinally welded heat exchanger tube. That is to say, in the case of the heat exchanger tube, a weld seam runs along the longitudinal extension of the tube and, when the tube is installed, it is arranged on the upper side of the tube cross section.

It has namely been shown that a layer, in particular coating, of a heat exchanger tube designed in accordance with the proposed concept is advantageously already applied to wide or narrow strips from which heat exchanger tubes are usually produced. Wide or narrow bands are band-shaped metal plates with the wall thickness of a heat exchanger tube, which are then rounded to form a slotted tube slotted along a longitudinal seam. This slotted tube is then provided along the longitudinal seam with a weld seam to create the heat exchanger tube. Since the layer provided in accordance with the concept of the invention, in particular coating, can possibly impair the welding process or the quality of the weld seam, the layer can be locally removed again in the area of the weld seam before the welding process. By removing the layer in the area of the weld seam, the above-described effect of the layer is impaired only to an insignificant extent, so that according to the concept of the invention, approximately 90% to 95% of the desired effects explained above are still achieved.

The layer is advantageously removed immediately before the welding process and while the strip is being formed into the slot tube in the area of the slot / weld seam.

A coating in the local area of the weld seam is expediently prevented by locally masking the weld seam area during the coating process. Alternatively or additionally, the weld seam area can be ground so that an existing layer, in particular coating, is removed again in the course of such a grinding process.

Subsequent installation of a heat exchanger tube, in which the weld seam is arranged along the longitudinal extension of the tube on the upper side of the tube cross section, i.e. in a twelve o'clock position, ensures that the weld seam not provided with a layer in such a case is less stressed by deposit formation than the side opposite the weld seam and the other areas of a heat exchanger tube. This advantageous measure therefore ensures that the welding process, which completes a slotted tube for the heat exchanger tube, is on the one hand not affected by a layer in accordance with the proposed concept, and on the other hand is particularly high Share of the desired effects explained above, advantageously in a range above 95 percent, is achieved.

The object with regard to a use relating to the heat exchanger tube is achieved according to the invention by using a layer material which reduces the adhesion of a fluid to a surface for an outer surface on an outside of a heat exchanger tube for exposure to a steam medium and for an inner surface on an inside of the heat exchanger tube for exposure with a cooling medium.

In particular, the outer surface is provided with a first layer which reduces the adhesion of the steam medium to the outer surface and / or the inner surface is provided with a second layer which reduces the adhesion of the cooling medium to the inner surface.

It has proven to be particularly advantageous that a material based on polytetrafluoroethylene (PTFE) as

Layer material is used. A material that contains PTFE in the form of Teflon can advantageously be used for this.

Furthermore, it has been shown that a material based on a carbon system is advantageous as a layer material. In particular, a material constructed according to a diamond-like system (DLC system) has proven to be particularly advantageous.

Furthermore, a material based on an organic silicate network for use as a layer material has proven to be particularly advantageous. Such organic silicate networks can advantageously be formed as an outer surface consisting of nanoparticles, which significantly reduce the non-stick properties of a surface, in particular an inner surface of the heat exchanger tube. Quite similar a DLC system surface on an inner surface of the heat exchanger tube proves to be particularly advantageous.

A layer material based on a polytetrafluoroethylene can be used particularly advantageously on an outer surface of a heat exchanger tube.

The use of all of the above-mentioned layer materials for a heat exchanger tube according to the concept explained above can be realized in a surprisingly advantageous manner according to the knowledge of the invention, because according to the usual measures, layers of the above-mentioned type could not be implemented on heat exchanger tubes and therefore could not be done by a person skilled in the art be considered.

Embodiments of the invention are described below with reference to the drawing. This is not intended to represent the exemplary embodiments significantly, rather the drawing, where useful for explanation, is carried out in a schematic and / or slightly distorted form. With regard to additions to the teachings which can be seen directly from the drawing, reference is made to the relevant prior art. The drawing shows in detail:

1 shows the cross section of a heat exchanger tube in the installed state according to a particularly preferred embodiment;

2 shows a schematic representation of a heat exchanger according to a particularly preferred embodiment with a cooling medium guide and a steam medium guide.

1 shows a heat exchanger tube 1 in the installed state in a heat exchanger, as is shown schematically in FIG. The particularly preferred embodiment of the heat exchanger tube 1 shown here in the installed state provides for the adhesion of a fluid to a surface 3, 5 of the heat exchanger. shear tube 1 reducing layer 7, 9 before. The heat exchanger tube 1 has an outer surface 3 on the steam side on its outer side 4 for the application of a vapor medium 25 and an inner surface 5 on the inside of the cooling medium on its inner side 6 for the application of a cooling medium 27. The outer surface 3 is provided with a first layer 7 which reduces the adhesion of the steam medium to the outer surface 3. The inner surface 5 is provided with a second layer 9 that reduces adhesion of the cooling medium to the inner surface 5.

In the present case, the first, steam-side layer 7 is made from a layer material which is a material based on a PTFE (polytetrafluoroethylene). In the present case, a mixture of Teflon and other components is preferred. In the present case, the second layer 9 on the cooling medium side is a material based on an organic silicate network. In the present case, this material was produced for the formation of nanoparticles by a so-called sol-gel process and thus has a surface structured in the nanometer range. It has been shown that this type of coating with a second layer 9 on an inner surface 5 particularly advantageously prevents the adhesive properties of a cooling medium and thus the deposition and accumulation of organic and inorganic material on the inner surface 5 of the heat exchanger tube 1. A first layer 7 on an outer surface 3 of the heat exchanger tube 1 based on polytetrafluoroethylene has a particularly low surface tension and thus reduces the formation of droplets on the surface and, if drops are formed, the dripping behavior is changed in such a way that no condensation films are formed can form the outer surface 3 of the heat exchanger tube 1.

The heat exchanger tube 1 shown in this embodiment is advantageously made from a narrow band, which already as such is assigned to the inner surface 5 Surface was provided with an organic silicate network of layer 9 to form an inner side 6 and was provided on a surface assigned to the outer surface 3 with a material based on polytetrafluoroethylene to form an outer side 4. As part of the further manufacturing process, the narrow band in area 11, i.e. at its edges, which would later lie in area 11 of the weld seam 13, was already masked during the coating process to form layers 9, 7 and was then sanded in this embodiment, so that the area 11 of the

Weld 13 remained coating-free. The grinding step can also be omitted as part of a modification. After the narrow band had been rounded to form the slot tube in the further production step, the weld seam 13 could be attached to the slot tube to complete the heat exchanger tube without having to accept the adverse effects of a coating 9, 7 on the welding process.

In the installed state, the heat exchanger tube 1 is installed in a heat exchanger 17 in the twelve o'clock position shown in FIG. H. the weld seam 13 is located on the upper side 15 of the pipe cross section.

As part of a modification, a heat exchanger tube, essentially using the same manufacturing method explained above, can only be coated in the region of its three o'clock position to nine o'clock position. It has been shown that the area around the six o'clock position in a heat exchanger tube is particularly susceptible to corrosion and deposits. In particular, often remain, for. B. especially when emptying the heat exchanger tube, suspended matter in the area of the six o'clock position on the inside of the heat exchanger tube. At least the area around the six o'clock position, e.g. B. a 45 ° angle range, a 90 ° angle range, advantageously a 120 ° angle range and in particular a 180 ° angle range or a larger angle range, is within the scope of the modification provided with a layer. 2 schematically shows a heat exchanger 17 with a cooling medium guide 19 and a steam medium guide 21. The cooling medium guide 19 has a plurality of heat exchanger tubes 23, which are explained in more detail in FIG. 1 and which are only shown schematically in FIG. 2, for guiding the cooling medium 27. The cooling medium 27 is guided on the inside 6 of the heat exchanger tubes 23. The steam guide 21 provides for the application of a vapor medium 25 to the outside 4 of the heat exchanger tubes 23.

In order to avoid film formation which hinders the heat transfer in heat exchanger tubes 1, 23, a heat exchanger tube 1, 23 has an outside 4 lying on an outer surface 3 for the application of a vapor medium and an inside 6 lying on an inner surface 5 for the application of a cooling medium according to the proposed concept that the outer surface 3 is provided with a first layer 7 that reduces the adhesion of the steam to the outer surface 3 and / or the inner surface is provided with a second layer 9 that reduces the adhesion of the cooling medium to the inner surface 5. The concept leads to a heat exchanger 17 and a use.

Claims

claims

1. Heat exchanger tube (1) with an outer surface (3) lying on the outside (4) for loading with a steam medium (25) and an inner surface (5) lying inside (6) for loading with a cooling medium (27), whereby the outer surface (3) is provided with a first layer (7) which reduces the adhesion of the steam medium (25) to the outer surface (3), and / or the inner surface (5) is provided with an adhesion of the cooling medium (27) to the Inner surface (5) reducing second layer (9), characterized in that the second layer (9) is designed as a layer which reduces the formation of deposits on the inner surface (5), the second layer being designed as a biocide layer.

2. Heat exchanger tube (1) according to claim 1, characterized in that the first layer (7) and / or the second layer (9) is formed by a number of sublayers.

3. Heat exchanger tube (1) according to claim 1, characterized in that in the case of a two-sided coating (7, 9) of the heat exchanger tube (1), the first layer (7) is different from the second layer (9).

4. Heat exchanger tube (1) according to one of claims 1 to 3, characterized in that the first layer (7) is designed as a layer reducing the surface tension of the outer surface (3).

5. Heat exchanger (17) with a cooling medium guide (19) and a steam medium guide (21), the cooling medium guide (19) having a plurality of heat exchanger tubes (23) for guiding cooling medium (27) on the inside (6) of a heat exchanger tube (1, 23), and the steam medium guide (21) is designed to act on an outside (4) of a heat exchanger tube (1, 23) with steam medium (25), characterized in that a heat exchanger tube (1, 23) according to one of the preceding claims is formed.

6. Heat exchanger according to claim 5, characterized in that the heat exchanger tube (1, 23) is designed as a longitudinally welded heat exchanger tube (1), in which a weld seam (13) runs along the elongated extent of the heat exchanger tube (1, 23) and in the installed state of the heat exchanger tube (1, 23) is arranged on the upper side (15) of the tube cross section.

7. Use of a layer material which reduces the adhesion of a fluid to an outer surface (3) on an outer side (4) of a heat exchanger tube (1, 23) for exposure to a steam medium (25) and for an inner surface (5 ) on an inside (6) of the heat exchanger tube (1, 23) for the application of a cooling medium (27).

Use according to claim 7, characterized in that the outer surface (3) is provided with a first layer (7) which reduces adhesion of the steam medium (25) to the outer surface (3), and / or the inner surface (5) is provided with a an adhesion of the cooling medium (27) on the inner surface (5) reducing second layer (9) is provided.

9. Use according to claim 7 or 8, characterized in that the layer material is a material based on PTFE (polytetrafluoroethylene).

10. Use according to claim 7 or 8, characterized in that the layer material is a material based on a carbon system.

11. Use according to claim 7 or 8, characterized in that the layer material is a material based on an organic silicate network.